The present invention relates generally to a method of packaging a semiconductor device and a semiconductor package and in particular embodiments, to such a method of packaging semiconductor device configured for dual sided cooling.
Packaging of a semiconductor device has at least two steps. First, a leadframe is connected to the semiconductor device for mechanical support and electrical connection. Secondly, the leadframe and the semiconductor device are molded to create the package. For example, a dual sided cooling package has a portion of the semiconductor device exposed on one side of the package, and a portion of the leadframe exposed on the opposite side. This allows heat transfer from both sides of the package, which improves thermal management.
A conventional leadframe package having dual sided cooling is described with respect to FIG. 5A. Referring to FIG. 5A, a two step interconnect process is used to fabricate the leadframe 500. In the first step, a chip 502 is attached to diepad 504 with either solder or adhesive 510. In the second step, the chip 502 is attached to leads 520 with either solder or adhesive 510. A mold 530 is filled in to form the leadframe 500.
A conventional flip chip package having dual sided cooling is described with respect to FIG. 5B. Referring to FIG. 5B, the chip 502 is attached to the leads 520 with solder 562. A mold 530 is filled in to form the flip chip package 550.
Referring to FIGS. 5A and 5B, the height h cannot be accurately controlled due to variation in thicknesses of each component, which has a deleteriously impact during subsequent molding process to form mold 530. However, the height of the molding cavity is fixed. If the height h is lower than a height of the mold cavity, a molding process forms mold flashes covering the leads 520. Removing the mold flashes to expose the leads 520 creates variation in package thickness. Alternatively, if the height h is higher than the height of the mold cavity, the chip 502 may be damaged during compression of the mold cavity during the molding process.